This application claims the priority of New Zealand patent application Serial No. 332331 filed on Oct. 15, 1998.
This invention relates generally to a process and apparatus for removing dissolved and undissolved solids from liquid mixtures.
presence of unwanted dissolved or undissolved solids or high boiling contaminants in process liquids can result in any one or a combination of the following difficulties; the contamination of sales products; the release of pollutants into the atmosphere and waterways; fouling or scaling of heat exchangers, reboilers, cooling circuits in internal combustion engines, other equipment and pipework; foaming in process equipment; high pumping or heating costs; inefficient energy use; accelerated corrosion or erosion; and/or undesirable chemical reactions.
The remedial measures required to restore satisfactory performance often include: batch extraction of the solids from the process streams; the use of additives to prevent or counteract foaming, corrosion and the like; purchase of replacement clean process liquid; the use of toxic or hazardous chemicals to remove fouling deposits and scale; shutdowns of the process plant to clean fouled equipment; and the repair or replacement of corroded or eroded items.
Furthermore, often the remedial measures increase the risk of polluting the environment because of the need to dispose of cleaning solutions, additives and contaminated process liquids.
It is an object of the present invention to overcome or substantially reduce in severity the above mentioned difficulties, or to at least provide the public with a useful choice.
In a first aspect the present invention provides a continuous process suitable for extracting dissolved and undissolved solids and/or high boiling point liquid contaminants from a mixture of miscible liquids in which at least one liquid component boils at a temperature substantially greater than the remaining liquid component(s), in which the undissolved solids and any precipitated dissolved solids are more dense than the liquid components of the liquid mixture, and in which the liquids remain free-flowing at a selected operating temperature and pressure throughout the process, the process including the steps of:
introducing a feed stream of the miscible liquid mixture into a separation vessel;
rapidly boiling or flashing the feed stream after mixing the stream with a recycle liquor to produce a vapour in proximity or within the separation vessel;
separating the vapour from the unvaporised components of the co-mingled feed stream and recycle liquor;
collecting the unvaporised liquid and solids in a substantially liquid pool in a lower portion of the separation vessel,
removing a recycle liquor stream from the liquid pool at a rate substantially equal to at least ten times the feed stream flow rate from a substantially upper portion of the liquid pool so as to obtain a recycle liquor containing a substantially low percentage of undissolved solids;
pumping the recycle liquor stream through a heat exchanger which rate of pumping is sufficiently high to maintain a significant flow rate of the recycle liquor through the heat exchanger;
supplying a sufficient heat flux to the recycle liquor in the heat exchanger such that the amount of heat added to the recycle liquor is sufficient to vapourise the feed stream when the recycle liquor and feed stream are mixed; and
extracting the solids and/or high boiling point liquids from the lower portion of the separation vessel.
In a further aspect the present invention provides an apparatus for removing dissolved or undissolved solids and/or high boiling point liquid components from liquid mixtures, the apparatus comprising;
a separation vessel, into which a feed stream of miscible liquid mixtures is delivered;
a solids extraction means located proximate to the separation vessel, which is adapted to extract the solids from the miscible liquids in the separation vessel,
a recycle circuit adapted to transfer a mixture of liquids in the form of a recycle liquor from the separation vessel through a heat exchanger located externally from the separation vessel, and back to the separation vessel, and in which the heat exchanger is dimensioned and adapted to provide heat flux sufficient to vaporise the feed stream when the recycle liquor and feed stream are mixed upon delivery into the separation vessel.